1. Field of the Invention
The present invention relates to a feed screw mechanism for displacing a displaceable body, which is screw-engaged with a feed screw shaft, along an axial direction under a driving action of a rotary drive source.
1. Description of the Related Art
Heretofore, a feed screw mechanism has been known, which is equipped with a screw shaft engraved with screw threads on an outer circumferential surface thereof, a cylindrical nut member disposed on an outer circumferential side of the screw shaft, and balls, which are disposed via the screw threads between the screw shaft and the nut member.
Such a feed screw mechanism, as disclosed in Japanese Laid-Open Patent Publication No. 2008-248938, is applied to an actuator, in which a displacement nut is fixed via balls to a slider that constitutes the actuator. In addition, by rotating the screw shaft under a driving action of a drive motor, the displacement nut is displaced in a straight line along the screw shaft, and together therewith, the slider, which is fixed to the displacement nut, also is displaced in a straight line.
However, in the conventional art described above, in the event that bending, warping or the like occurs in the screw shaft that constitutes the feed screw mechanism, or if variances occur due to product differences or assembly errors in the screw shaft and the displacement nut, defects in operation of the displacement nut caused by such variances tend to occur. Thus, in order to resolve and eliminate the aforementioned operational defects, when the screw shaft and the displacement nut are assembled, work to perform adjustments thereon is required, thereby complicating assembly operations of the feed screw mechanism.